I've heard that, supposedly, the original voicework sounds better to sub fans because they aren't native japanese speakers, and it's harder to tell when the voice acting is on or off, so to speak.
The sub voices could be just as bad (or good) as the dub, but that's apparently harder to tell for someone who didn't grow up with the language.
This is definitely possible and highly likely, although i've watched so much Anime that i'm actually picking up some moonspeak, i have no doubt that the fact that it's not my native language means that i can't tell when the bad voice acting is bad.
The other thing is of course that in Wapan, being a Seiyu is considered a pretty serious profession and is often used by wannabe singers to jump-start their career, wheras in the western world outside of CGI movies (and often even in them) voice acting has a far less professional and glamorous position.
As Pixar have shown; it is possible to get good VA's in western media, but as Dreamworks have shown; it's
really hard and basically requires hiring actual actors and movie stars, which is ridiculously expensive.
Basically, voice acting has a higher level of professionalism in Japan than it does in the west, which i suspect is one of the key reasons why Japanese voice acting tends to be leagues ahead of most western voice acting (at least the english stuff, can't really say for French or anything like that.) more often than not.